A specific chromosomal translocation, the Philadelphia translocation, is characteristic of over 96% of patients with chronic myelocytic leukemia. This translocation involves the transfer of the c-abl oncogene from chromosome 9 to a specific region, designated the breakpoint cluster region (bcr), on chromosome 22. The resulting gene encodes a chimeric mRNA and presumably a chimeric protein containing 5' bcr and 3' c-abl specific domains. Three bcr homologous genomic sequences have recently been identified, two of which have been localized to chromosome 22. The major objective of this project will be to test the possible involvement of bcr homologous sequences in a broad range of human cancers, with emphasis on those, such as Ewing's sarcoma, which are known to involve chromosome 22 translocations. In Phase I, genomic DNA sequences representative of each of the three newly identified bcr homologous regions will be molecularly cloned and compared by restriction endonuclease analysis. Phase II experiments will be designed to prepare genomic and/or cDNA probes specific for each, and to systematically screen human tumor DNAs and DNAs of patients with specific hereditary disorders for bcr-related sequence alterations of potential diagnostic significance. (U)